I'd like to remind all of you, that there is a wonderful tool you can use to solve a lot of software problems on Xperia devices.
It is called "Flashtool", it was originally developed by Bin4ry and it is maintained and developed by Androxyde.

●► Use:Flashtool is most commonly used to flash original Sony stock firmwares to your phone and to unlock and relock the bootloader.A big pro is, you can flash firmwares no matter the bootloader status. PC Companion and SEUS need a locked bootloader.

A lot of users in the Q&A and General Forums are stuck with boot loops or bricked Xperias after flashing stuff to their device.
Sometimes a stock Sony firmware refuses to boot after installing something or just out of nowhere. You might also have the problem that
PC Companion and SEUS don't want to update to the newest firmware. Or maybe your phone doesn't have any signal and can't connect
to the network or Wi-Fi. Sometimes the SIM card is not recognized. Or you have to send it in to repair service and it is rooted and has an
unlocked bootloader. Or you just simply want to sell it.
Even problems with the hardware like sensors that don't work properly (cameras, rotation, gps, compass, etc.) or even problems with
the mic, screen and battery can be solved by just flashing a stock Sony firmware.
Do you want to create your own .ftf file to upload to XDA or share with your friends? Flashtool can do that as well.
You can also use it to flash just the kernel in order to root a newer firmware.

You will find those .ftf files on the xda forums for download.

So, before you panic and think about sending your phone in for repair, try to use this tool, it's a lot faster and it often solves the problem

●► How to:
After installing Flashtool, you will have to install the drivers. You can find the "drivers" folder inside the flashtool install directory.
Also try these drivers. In order to install unsigned drivers in Windows 8 and 8.1 use this guide.

You will also find a folder called "firmwares" in the flashtool install directory. Thats where you have to put the .ftf files.
Then start Flashtool.
Click the flash button and choose "Flashmode".
In the list below you will see all firmwares and kernels inside the "firmwares" folder.
Choose the one you want to flash.Leave everything else as it is!
Click the "Flash" button in the right corner.

Now Flashtool prepares the files for flashing. A prompt will pop up telling you to power off your phone and connect
in flashmode by pressing the back button.On newer Xperia devices you have to press the Vol-down button while connecting the USB cable.
The flashing process will start.Do not disconnect the USB cable until its done!
When everything is done, unplug USB and power on the phone.

If you want to flash just a kernel.ftf, you will find the right procedure in the kernel thread.

●► Reminder:
You have to keep in mind, that flashing an .ftf firmware file with Flashtool will factory reset your device!
System partition, apps and settings and even the internal storage will be wiped after flashing!
(You have the option to not wipe those, but in order to get rid of all problems you should wipe everything)
And that's where the nandroid backup comes into place:
You should always have a backup of a working system. It saves you a lot of trouble and installation procedures..
After flashing the firmware you can use the backup to put all your settings back into place.

●► Last but not least:
There is another, official "Flashtool" by Sony, don't mistake it for this one!

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